1. Field of the Invention
The present invention relates to a plasma display panel (PDP) and a method for manufacturing the same.
A PDP has received attention as a slim display device having a wide viewing angle. As being used widely as a HDTV, a high performance PDP with higher luminance is desired.
2. Description of the Prior Art
An AC type PDP that is commercialized as a large screen display device for a television set is a surface discharge type. The surface discharge type means a type of structure in which first and second display electrodes to be anodes and cathodes in display discharge, i.e., main discharge for ensuring a certain luminance are arranged in parallel on the front or back substrate. In the surface discharge type, a fluorescent material layer for a color display can be disposed away from a display electrode pair in the direction of the panel thickness so that deterioration of the fluorescent material layer due to an impact of ions in the discharge can be reduced, thereby a long life color screen can be realized.
An electrode matrix structure of the surface discharge type is typically a xe2x80x9cthree-electrode structurexe2x80x9d in which address electrodes for selecting cells are arranged so as to cross the display electrodes. In a basic form of the three-electrode structure, a pair of display electrodes is arranged for each row of a screen. An arrangement space (a surface discharge gap length) of a display electrode pair in each row is set to a few tens of microns so that discharge can be generated in response to application of a voltage at approximately 150-200 volts. In contrast, an electrode gap between neighboring rows (called a reverse slit) is set to a value sufficiently (a few times) larger than the surface discharge gap length for preventing an undesired surface discharge between rows and for reducing a capacitance. Namely, the arrangement space between the display electrodes in a row is different from the arrangement space between the display electrodes of neighboring rows. In this basic form, the inverted slit does not contribute to light emission, so a usage ratio of the screen is small. This means a disadvantage in luminance and a difficulty in high definition by reducing the row pitch.
As another form of the three-electrode structure, there is an electrode structure in which N+1 display electrodes (N is the number of rows of a screen) are arranged at a constant pitch, and surface discharge is generated between neighboring electrodes making an electrode pair. In this way, the usage ratio of the screen can be enhanced. However, since each display electrode except both ends of the arrangement works for two rows, a driving sequence for addressing for setting display contents becomes more complicated than the basic form.
In the conventional PDP, the display electrode is formed by patterning a conductive thin film formed on the substrate. Namely, the surface of the display electrode is substantially parallel with the surface of the substrate. Furthermore, in the cell structure (called a reflection type) in which the fluorescent material layer is disposed at the back side of the discharge gas space, the display electrode is a lamination including a wide band-like transparent conductive film and a narrow band-like metal film for compensating the conductivity of the transparent conductive film, so as to reduce the light shield by the electrode.
Conventionally, the surface discharge gap length is shorter than one fourth of the column direction size of a cell, and a positive column that provides high luminance rarely appears in the surface discharge. Therefore, there is a problem that the light emission efficiency is low. There is another problem that wasteful power consumed in charging a capacitance between the display electrodes is large. Since the power consumption is apt to increase as a high definition is progressed, it is important to reduce the power consumption also for heat control. In addition, since the display electrode includes the transparent conductive film and the metal film in a reflection type, there are problems of increase of the number of manufacture process due to usage of the different materials and increase of possibility of occurrence of an exfoliation at an interface between the films.
An object of the present invention is to provide a PDP having a novel cell structure that is superior in light emission efficiency. Another object is to provide a method for manufacturing a PDP having a novel cell structure with high productivity.
The present invention provides a plasma display panel in which a conductive film to be display electrodes is formed on the side portions of the wall, so that a main surface that contributes to discharge in the display electrode is substantially perpendicular to surface of the substrate and is opposed to another main surface of the neighboring display electrode via a gas space. A power supplying portion straddling plural cells in the display electrode is disposed on the upper surface of the wall. Namely, the display electrode (the conductive film) has a shape straddling the top portion and the side portions of the wall. In addition, to suppress discharge between the power supplying portions of the neighboring display electrode and to make discharge between the main surfaces generate easily, the display electrode is covered with a dielectric layer that is thin at the side portions and is thick at the top portion of the wall.
The discharge form is the opposed discharge between the electrodes that sandwich the gas space (however, the charge movement direction is not the panel thickness direction but is the direction along the surface of the substrate). This discharge form is called xe2x80x9csurface direction opposed dischargexe2x80x9d. Since the distance between the display electrodes is large in the cell structure of the present invention, discharge with high luminance in which a positive column extends can be generated, and capacitance between display electrodes can be reduced substantially. In addition, by selecting the area and the shape of the main surface of the display electrode at the side portions of the wall, discharge current can be optimized and the light emission efficiency can be improved.
The dielectric layer is formed by the thick film method, and plural types of pastes having different flowability are used so as to obtain a layer that is thick partially. Glass paste having low flowability by adding filler is applied to the portion to be thick (the top portion of the wall), and glass paste having high flowability is applied to the entire wall including the portion to be thick for forming the thin portion.